The present invention relates to a fuel supply device for an internal combustion engine of a motor vehicle.
One of such fuel supply devices is disclosed for example in the German patent document DE28 08 731 C2. The fuel supply device has a feeding aggregate which is driven by an electric motor and feeds the fuel from a supply container to an injection device of the internal combustion engine. Moreover, a pressure sensor is provided which determines the fuel pressure downstream of the feeding aggregate. The pressure sensor is connected with a control device which controls the operation of the electric motor of the feeding aggregate, so that the fuel pressure downstream of the feeding aggregate is at least approximately equal to a predetermined nominal pressure. The feeding aggregate therefore feeds only the fuel quantity which is consumed by the internal combustion engine, so that no return quantity is supplied back from the internal combustion engine to the supply container. A throttled discharge is provided downtream of the pressure sensor so that during the operation of the feeding aggregate, a partial quantity of the fuel fed by it is discharged. This enables an operation of the feeding aggregate also when the fuel consumption of the internal combustion engine is very small. In particular, during and after the start of the internal combustion engine, the feeding aggregate does not provide the full feeding power, and a partial quantity of the fuel fed by the feeding aggregate is discharged through the throttle discharge so that in this condition the fuel quantity supplied by the internal combustion engine is not sufficient. Moreover, due to the throttled discharge with the switched off internal combustion engine, fuel is discharged so that the fuel pressure in the injection device of the internal combustion engine is decreased.
Accordingly, it is an object of present invention to provide a fuel supply device for an internal combustion engine of a motor vehicle which avoids the disadvantages of the prior art.
In keeping with these objects and with others and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a fuel supply device of the above mentioned general type, in which the discharge is controlled by a valve device in dependence on the fuel pressure, and the valve device opens the discharge in response to exceeding a fuel pressure located under the nominal pressure, and also a check valve is integrated in the feeding aggregate.
When the fuel supply device is designed in accordance with the present invention, it has the advantage that the throttle discharge is first open by the valve device when the fuel pressure reaches at least approximately the predetermined nominal pressure, so that in particular at and after the start the total fuel quantity fed by the feeding aggregate is supplied, to the internal combustion engine. Moreover, the valve device guarantees that with the shut off internal combustion engine, the throttled discharge is closed and the fuel pressure in the injection device is maintained at least approximately at the predetermined nominal pressure. When a pressure increase occurs with the shut-off internal combustion engine due to a heating of the fuel, it can be unloaded due to the valve device.
In accordance with another advantageous feature of present invention, a fuel filter is arranged between the feeding aggregate and the pressure sensor, so that the pressure sensor determines the fuel pressure downstream of the fuel filter. In this construction the pressure sensor determines the actual fuel pressure in the injection device which, for example due to a dirtying of the fuel filter, can be lower than the fuel pressure upstream of the fuel filter.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.